Catheters intended for use with guidewires have a distal tip with an inner diameter that is slightly larger than the outside diameter of the intended guidewire. The difference in diameter is necessary to provide the guidewire with operating clearance. When navigating tortuous anatomy or crossing a previously deployed stent, the guidewire is not concentric with the distal tip of the catheter due to this required clearance. Because of this required clearance, the distal tip of the catheter protrudes along the outer meridian of a severely bent catheter/guidewire assembly, with the result that it is at risk of catching on the vessel wall and consequently impede trackability of the catheter over the guidewire. This can result in an increase in the time of the procedure as the medical practitioner may be forced to withdraw the catheter and again attempt to maneuver the assembly through the tortuous anatomy responsible for the severe bend. Likewise, if the catheter tip catches on the luminal surface of the vessel wall, damage to the luminal surface may result, requiring surgical intervention. Similarly, the catheter tip is also at risk of catching on the struts at the end of a previously deployed stent, thereby impeding crossability.
There have been various catheter designs in the art that describe centering concepts that relate to the tip of the catheter. U.S. Pat. No. 5,122,125 to Deuss teaches a guiding catheter having a tip portion with external ribs intended to center the catheter within the vessel it is being moved through. U.S. Pat. No. 6,228,110 to Munsinger describes a catheter with a tip portion including a series of bristles affixed to the luminal surface of the tip. The bristles are intended to serve as an axial brake designed to inhibit unintended axial motion between the catheter and a guidewire within the catheter. The concentric design of the bristles serves to center the guidewire within the catheter tip. However, the group of bristles are located some distance proximally from the distal end of the catheter, with the result that while an effective axial braking means is provided between the catheter and guidewire, the guidewire is not centered as it exits the distal end of the catheter.